Authenticating Your Twitter Account with Twitterrific (Mac & iOS)

Why am I sent to an authentication webpage when adding a
new Twitter account in Twitterrific?

Twitter recently changed their authentication requirements for
third-party applications that access direct messages. In order for
Twitterrific to send and receive DMs, Twitter requires that you
approve access for the app using their OAuth webpage. Once you
allow access there, you'll be taken back to Twitterrific.